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1X19 stretch

Discussion in 'Ask All Sailors' started by capta, Jan 12, 2018 at 6:14 PM. Add this thread to a FAQ

  1. capta

    capta

    Joined Jun 4, 2009
    2,096 posts, 384 likes
    Pearson 530
    XX Sailing in the Windward or Leeward Islands where ever we are anchored
    My wire is pretty tight. I can't get more than a couple of inches of deflection on the uppers or intermediates when I really pull hard, using my weight. ½" 1X19.
    Up to 20 knots to weather the leeward shrouds stay at least straight (firm), but above that they get a little to quite a bit slack, but the mast remains straight, and it does not move around aloft or at the deck. This is a massive, double section Hood Stoway mast, capable of freestanding for a bit, if a shroud broke, according to one rigger I talked to back when I bought the boat.
    I really can't imagine 1X19 ½" ss wire would stretch that much in around 65', but that's why I'm posting. I also can't imagine tightening my rig much more.
    Any thoughts from you engineers, racing sailors or riggers out there would be appreciated.
     


  2. SG

    SG

    Joined Feb 11, 2017
    690 posts, 96 likes
    J/Boat J/160
    US Annapolis
    At some point the sag is out of the forestay -- then you're going to be compressing the mast...
     


  3. Ted

    Ted

    Joined Jan 26, 2005
    959 posts, 112 likes
    C&C 110
    US Bay Shore, Long Island, NY
    Have you been able to put a tension gauge on those monster shrouds? Don't try and guess if your tension is correct. You'll be surprised at how incorrect that can be.
     


  4. capta

    capta

    Joined Jun 4, 2009
    2,096 posts, 384 likes
    Pearson 530
    XX Sailing in the Windward or Leeward Islands where ever we are anchored
    No gauge that big available anywhere in the Caribbean, as far as I know.
     


  5. SG

    SG

    Joined Feb 11, 2017
    690 posts, 96 likes
    J/Boat J/160
    US Annapolis
    Do you have sag on the head stay when beating?
     


  6. capta

    capta

    Joined Jun 4, 2009
    2,096 posts, 384 likes
    Pearson 530
    XX Sailing in the Windward or Leeward Islands where ever we are anchored
    Sag?
     


  7. SG

    SG

    Joined Feb 11, 2017
    690 posts, 96 likes
    J/Boat J/160
    US Annapolis
    lIf you sight up you forestay while beating into a breeze, with the jib loaded up, you would see that the forestay isn't straight, it's "arced" a bit. If it's arced that's what I call "sag". You can take out some of the sag, to the extent that Jour have the means to tension the backstay. If your firestay is so tight that there is little sag, then you will do little but add a bunch of not useful compression to the mast. Of course your BIGGEST Pearson doesn't have most flexible rig ;^)))
     


  8. David in Sandusky

    David in Sandusky

    Joined Nov 8, 2007
    971 posts, 64 likes
    Hunter 27_75-84
    US Sandusky Harbor Marina, Lake Erie
    Get a Loos gauge and measure the tension in your rig. It’s not an expensive item and light enough to easily ship to you.

    A properly tensioned rig will not be slack to leeward in any reasonable sailing conditions.
     


  9. kloudie1

    kloudie1

    Joined Nov 6, 2006
    7,469 posts, 371 likes
    Hunter 34
    US Mandeville Louisiana
    Here is some info: http://www.loosco.com/resource-library/technical-information/cable-wire-rope-stretch/
    The calculator/approximate is in % of total length.. pretty much indicates that wire attachment flex or hull deformation under load may be coming into play here.. Without knowing the loads on the shrouds it is hard to guesstimate.. Thumbnail numbers look to be in the 1/8" range for a nominal 55 foot long shroud.. Think of the shrouds as two springs .. with equal but not much stretch, as soon as the windward spring stretches a little, the mast top moves leeward and unloads the other spring so it goes loose.. the other case is that the springs have a lot of stretch in them (high preload) and when the windward stretches a little more from wind load, the amount of stretch in the leeward shroud decreases but its preload stretch is sufficient to not let it go slack.. dunno if this helps or helps muddy the water??
     


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  10. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    838 posts, 246 likes
    O'Day 19
    US Littleton, NH Littleton, NH
    How to Tune a Sailboat Mast
    taken from The Rigging Company (link is at the bottom)

    March 22, 2016 at 10:27
    I have rod rigging on my Beneteau 32s5
    Any other guidance on tuning them vs wire rigging

    Reply
    • [​IMG]The Rigging Company, LLP says:
      March 22, 2016 at 14:05
      Hi and thanks for commenting.

      Just follow the guidelines in the write up. The over all goal is that the mast needs to be straight and in-column when looking at it from side to side.

      Fore and aft, the mast should show a very slight lean aft. Depending on whether or not the spreaders are in-line or aft swept; you should also see some slight bend if there is any aft sweep to the spreaders just from the tension of the uppers.

      A Rod stay tends to run a bit tighter than wire, so keep that in mind.

      For racing, ideally once the static tune at the dock (the part we just talked about) is done, go out and sail tune. Do this by going hard on the wind and checking to see if the leeward shrouds are just starting to dance, this is ideal. If they are swaying about they are too loose for the current conditions. If the leeward shrouds are tight, they may be a touch to tight. Tension and loosen as needed; count what you did and to what shroud, then tack and do the same to the other side.

      ALWAYS secure the turnbuckles when you are finished adjusting them.

      Hope that helps.

      ~T.R.C.


      https://theriggingco.com/2017/01/21/how-to-tune-a-sailboat-mast/


      • A VERY interesting read.

      • -Will (Dragonfly)
     


  11. capta

    capta

    Joined Jun 4, 2009
    2,096 posts, 384 likes
    Pearson 530
    XX Sailing in the Windward or Leeward Islands where ever we are anchored
    LOOS Cable Tension Gauges offer ±5% accuracy in measuring cable tension on the standing rigging of sailboats as well as architectural railings. Choose the model you need to measure cable diameters from 3/32" to 3/8" and Rod diameters from .172 up to .375
     


  12. smokey73

    smokey73

    Joined Oct 26, 2010
    480 posts, 75 likes
    Hunter 40.5
    US Beaufort, SC
    Klondie, I might be doing something wrong with my numbers but I got a different amount of stretch for a 1/2 inch SS steel wire. If I recall the loose gauge instruction, the object is to get about 10% of breaking strength pre-loaded onto the shroud as an initial setting.
    Using the Loos calcualtor
    Breaking Strength = 30,000 lbs
    Use Preload of 3000 lbs (10%)
    Use diameter of .5 inches
    They only list 302/304 SS and galvanized so use 302/304
    Plug that in and it yields .0935% stretch
    Use 55 feet (although I think Capta said a 65 foot mast but that may be from the water line)
    55 feet X 12 in/ft = 660 inches
    Stretch under pre-load is 660 x .0935/100 = .6171 in or about 5/8 inch
    This is the amount the 1/2 inch 1X19 302/304 SS wire would stretch under the preload. (If its 316 I think its more elastic and would stretch more but its breaking strength is less)

    Now using different loads induced while under load sailing (I have no idea how to calculate what those loads might be)
    At 6000 lbs total load- additional stretch is .6171 inches (20% breaking strength is normally safe working load)
    At 10000 lbs total load - additional stretch is 1.44 inches
    At 12,000 lbs total load - additional stretch is 1.85 inches

    As you said, there are a lot of variables here like bending strength of the mast (as mentioned by Capta), the load imposed when beating, angle of the shroud to the mast, etc. However, with the considerable load that a large sail area can impose on a mast, I would expect the loads on the shroud to be in the 6000 lb to 10000 lb range (only a wild guess though). I seem to recall reading in a rig tuning guide that under a strong wind beating it is not unexpected that the lee shrouds would be "slack", not flopping in the wind, but no longer taught. Others may be able to add their experiences and thoughts. Note that at 6000 lbs total load (20% breaking strength) the imposed load would take the pre-load off the lee shroud making it "slack". Sounds like a good design to me and that is what I'd expect for design expected load under sail. (It might be more under extreme conditions or gusts)

    Also - I am not sure that Loos makes a rigging gauge that goes all the way up to 1/2 inch. The largest size I saw, even in the professional series was only 3/8 inches. May need to call Loos directly to get a way to measure it?
     


    Last edited: Jan 13, 2018 at 6:32 AM
    kloudie1 likes this.
  13. SG

    SG

    Joined Feb 11, 2017
    690 posts, 96 likes
    J/Boat J/160
    US Annapolis
    I didn’t read the original post correctly. I was dealing with the forestay in my suggestions above for this situatiin, Capta

    Have you tried tightening the stay(s) slightly to take the slack out when sailing? i .e, the leeward ones. If the mast stays in column at rest, and on both tacks, and the stays aren’t clearly loose, I would think that some minor adjustments should work.

    You don’t have anything loose up there so it’s moving?
     


  14. smokey73

    smokey73

    Joined Oct 26, 2010
    480 posts, 75 likes
    Hunter 40.5
    US Beaufort, SC
    Capta, are your shrouds 302/304 1X19 or 316 1X19 SS? I would expect them to be 302/304 but if you had them custom made they may be 316 SS.

    All the numbers I gave would need to be adjusted for that difference if they are 316 SS. The formula should be the same, the difference being the "G" number used in the calc and the breaking strength for 1X19 316 SS. Lacking any other info I'd use 10% breaking strength as the pre-load. You may be able to get the breaking strength from the wire manufacturer who made your shroud wires. I'd use the manufacturer who made your shroud wires if you can. Loos may not even answer the question if they did not make the wire (liability issue for them)

    By the way, "I'm not an engineer but I slept in a Holiday Inn last night" - Oh wait, I am an engineer but I am not a "Structural Engineer" nor a rigger so I'd take what I have posted with a grain of salt until you get better info. My info on rig tuning (slack on the lee side) comes from the Selden rig tuning guide. With your mast, which I believe you said was a thick walled Hood Stoway the tuning guide may be different. I'd contact them, they should have a comparable rig tuning guide to the Selden guide.
     


    capta likes this.
  15. kloudie1

    kloudie1

    Joined Nov 6, 2006
    7,469 posts, 371 likes
    Hunter 34
    US Mandeville Louisiana
    Egg Zachery correct, Smokey73.. I read 1/2" diameter and was thinking 1" and thinking "man that is big wire"
    More coffee, please. I used to calculate rigging but I am just an olde retired fart now!
     


  16. smokey73

    smokey73

    Joined Oct 26, 2010
    480 posts, 75 likes
    Hunter 40.5
    US Beaufort, SC
    Capta, I'm sure you know this but keep in mind the tension on the lower shrouds is typically less than the tension on the upper shrouds. With all the twists and turns (pun intended) in tuning I'd see if you can contact Hood for their tuning instructions to be safe. Still, I'm pretty sure the lee shrouds should not be "flopping around" when beating.
     


    capta likes this.
  17. SG

    SG

    Joined Feb 11, 2017
    690 posts, 96 likes
    J/Boat J/160
    US Annapolis
    The criteria for safe working load (some rule of thumb fraction of maximum beaking strength) isn’t necessarily where you want to tension the rigging. You want to stay UNDER that amount?
     


    Will Gilmore likes this.
  18. smokey73

    smokey73

    Joined Oct 26, 2010
    480 posts, 75 likes
    Hunter 40.5
    US Beaufort, SC
    Capta - I am not sure of the rig type, masthead, fractional, etc of your boat. From the look of your picture it seems that your spreaders are not swept back. Here is a link to the Loos guage manual on how to use the PT Series Loos gauge that should be of some help if you don't already have it. The long and short of it for a rig without swept back spreaders is that INITIAL tension should be about 10% of breaking strength. Then you go sailing and adjust the shrouds so that when close hauled in a reasonably brisk wind your lee shrouds don't go slack (I've been using the term "slack" to mean under just under very little tension but not "loose" - might be the wrong term though).

    https://loosnaples.com/how-to-use-pt-series-tension-gauges

    You're way past the initial setting phase and your mast hasn't come down yet so it seems you should be able to go directly to the "sailing close-hauled in a reasonably brisk breeze." step and adjust the tension in small steps until you reached the desired condition. A there may be some "creep" in the wire after extended load in tension so its a good idea to do this periodically anyway for optimum mast tuning.

    Hopefully Klondie will weigh in on this and give his perspective. I would take his advice over mine (not withstanding the lack of coffee math error -1 pt Correct for Data error)
     


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  19. smokey73

    smokey73

    Joined Oct 26, 2010
    480 posts, 75 likes
    Hunter 40.5
    US Beaufort, SC
    Correct. That is why the Loos tuning guide says an initial tension of 10% to 12% of breaking strength, not 20%. However, for some rig types (swept back rigs) the Loos guide does go up to 20% :yikes: as the initial setting but with a caution to never exceed 25% of breaking strength.
     


  20. capta

    capta

    Joined Jun 4, 2009
    2,096 posts, 384 likes
    Pearson 530
    XX Sailing in the Windward or Leeward Islands where ever we are anchored
    I used to tune my Rhodes racer (wooden stick) like stated above, but I had sheltered water and a stiff breeze to do it in. Down here the only place I get enough wind is sailing between islands, with some seas (3 to 6 feet in 20k). That is why I have been hesitant to tune her like that.
    I shall contact Hood Monday, given that the internet is working, and see what they say.
    As for wire type, your guess is as good as mine. Some places it tarnishes, some not, on the same wire.
    In the early days of glass boats and alloy masts, there were lots of dismastings, before 'they' figured out that these masts needed compression. Then they started punching the masts through the boats' bottoms. Perhaps an irrational fear these days, but hey, everyone has one or more of those, don't they?
     



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